It's just another language. Different for each type of animal, but they all communicate in one form or another. If you spend enough time with one, you can learn to understand what they're communicating at least to some extent. I don't believe this has anything to do with Autism though. Plenty of NT's are capable of it too.
What does make this kind of interesting in relation to Autism is the fact that vocal intonations and body language are actually much more important in the animal realm. Which makes me wonder if Autistics are any better at it than NT's. From what I've seen of my own kids, I don't think we are. I have to tell them to leave the damned cats alone all the time because they don't see that they are getting irritated.
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I'm not likely to be around much longer. As before when I first signed up here years ago, I'm finding that after a long hiatus, and after only a few days back on here, I'm spending way too much time here again already. So I'm requesting my account be locked, banned or whatever. It's just time. Until then, well, I dunno...